Niacin (Vitamin B3) - Benefits, Deficiency Symptoms And Food Sources

Alternative name :: Vitamin B3, Nicotinic Acid, Niacinamide

Niacin deficiency disease pellagra was first identified in 1735 by Casals. After extensive research, Goldberger held in 1918 that the cause of the disease was due to nutrient deficiency. However, it was in 1937 that Elvehjem ascertained that pellagra was caused due to deficiency of a water-soluble B vitamin, called niacin.

Niacin is the generic term for two compounds, nicotinic acid and nicotinamide. Both have equal biologic activity and potency. It was also established early that the amino acid tryptophan gets converted to niacin in our body. Thus, a diet liberal in protein would provide enough niacin even though the diet may be low in niacin. In the body, 60mg of tryptophan yields 1mg niacin. Since the body obtains niacin both from diet and from the amino acid tryptophan, niacin value is expressed in terms of niacin equivalents (NE).

1NE=1mg niacin=60mg tryptophan

Being water-soluble, niacin is directly absorbed from the small intestine. The body does not have large reserves of the vitamin and it should be supplied regularly in the diet. Any excess the vitamin is excreted in the urine.

Niacin is moderately soluble in hot water. It is very stable to heat, light, oxidation, acids and alkalis. Even boiling and autoclaving does not destroy it.

Vitamin B3 benefits and functions

Like other B-complex vitamins, niacin is a constituent of coenzymes involved in important metabolic pathways such as oxidation of glucose, fat synthesis and in tissue respiration. However, niacin is also used as a drug in treatment of some disorders.

Vitamin B3 helps to maintain a healthy skin . Niacin dilates the blood capillary system. This vitamin is also essential for synthesis of the sex hormones, namely, oestrogen, progesterone, and testosterone, as well as cortisone, thyroxin, and insulin. It also maintains mental and emotional well-being .

Niacin as a constituent of coenzymes

Niacin is a partner with riboflavin in the cellular coenzyme systems. In these systems the oxidation of glucose often takes place in the absence of oxygen simply by the removal of hydrogen ions. These ions are passed down the line from one compound to another to the eventual receiver oxygen, forming water and carbon dioxide. The two niacin coenzymes that operate in these metabolic reactions are NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate). NAD and NADP act as coenzymes for more than 200 enzymes involved in the metabolism of carbohydrates, fatty acids and amino acids.

NAD and NADP are hydrogen acceptors involved in a large number of oxidation-reduction reactions. On accepting hydrogen, they become NADH and NADPH respectively. In general, NAD is involved in catabolic reactions and NADP an anabolic (synthetic) reactions.

Niacin as a drug

Pharmacologic doses of niacin are used in cardiovascular diseases to lower elevated serum cholesterol and triglycerides. However, niacin should be used with caution as a drug because it can produce side effects such as skin flushing, itching, tingling sensation and gastrointestinal disturbances.

Daily allowances of niacin

The minimum Recommended Dosage Allowance of Vitamin B 3 are :-

• Men - 19 mg.
• Women - 15 mg.
• Pregnant women - 17 mg.
• Lactating women - 20 mg.

Because of the extreme nausea that accompanies large doses of niacin, there are few reported cases of individuals taking enough niacin to overdose.

Rich sources of niacin

A regular healthy diet including protein usually supplies the appropriate amount of Vitamin B3 to keep the body in good working order. Niacin and niacinamide are found in beef liver, brewer's yeast, lean meats, poultry, fish, eggs, cheese, soybeans, nuts, whole grains, green vegetables, cooked dried beans, and milk (non- or low fat milk). Vegetables should be baked, steamed or prepared as stir-fry to retain Vitamin B3.

Deficiency Symptoms of Vitamin B3

Pellagra, the disease caused by a vitamin B3 deficiency, is rare in Western societies. Symptoms include loss of appetite, skin rash, diarrhea , mental changes, beefy tongue, and digestive and emotional disturbance.